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The following two images (and animation) shows the processed synthetic aperture radar (SAR) data acquired before and after the explosion of the Anak Krakatau volcano. The two SAR data were acquired on two different satellite passes (ascending and descending respectively).

Following the explosion a landslide into the ocean of part of the volcano and the island led to a tsunami (concentric waves around the island can be seen in the after image). The two images are followed by an animation and a video.

Researchers at Caltech made the animations below which show the seasonal deformation and subsidence of Earth’s surface, respectively, as a result of groundwater extraction and refilling. This occurs when soil and earth layers are compacted and undergo subsidence due to the decrease of upward hydrostatic pressure balancing the weight of the layers.

Surface deformation and subsidence of Earth’s surface is measured using Interferometric Synthetic Aperture Radar (ISAR). ISAR is also used for natural hazard assessment. This includes applications to regions of volcanic, tectonic (e.g. faults and mountains), and construction activities.